Mobile terminal with electromagnetic actuator

ABSTRACT

This invention deals with a portable terminal that reduces extraneous tones in a portable terminal in which is mounted an electromagnetic induction actuator that produces voice signals, a buzzer signal or a low frequency vibration. By short-circuiting the terminal fittings of the electromagnetic induction actuator or by connecting them electrically to amplifiers or to a signal generator that produces a constant voltage signal or a constant-frequency signal, the extraneous tone produced by vibration of the mechanical vibration system of the actuator is reduced.

FIELD OF INDUSTRIAL USE

This invention deals with a portable terminal in which is mounted anelectromagnetic induction actuator that produces a communicant voice, abuzz, a melody or a low frequency vibration, in accordance with thefrequency of an electric signal.

PRIOR TECHNOLOGY

In recent years the growing popularity of portable terminals, asrepresented by portable telephones, has been remarkable. As means ofincoming call notification, these portable terminals have been fitted,normally, with small, cylindrical motors for generation of vibrations tobe sensed by the body, transducers to create a buzzing sound, andspeakers used for communicant voice signals.

Because there is generally a strong preference for miniaturized portableterminals, efforts have been made to reduce the number of parts mountedwithin the terminals. As a specific example, an electromagneticinduction actuator 1, shown in FIG. 8, has been proposed and put intopractical use. In this electromagnetic induction actuator 1, a platemagnet 24, a yoke 25 and a pole piece 23 make up a magnetic circuit 9that is supported by two leaf-spring suspensions 21, 22 within acylindrical housing 19 to constitute a magnetic vibration system 6.

A voice coil 8 is attached to a diaphragm 18 that is fitted and fixedinto the open end of the housing 19, input terminals are formed byplacing terminal fittings 3, 3′ on a terminal seat 20 that projectsoutward from the side of the housing 19, and the voice coil 8 isconnected electrically to the terminal fittings 3, 3′.

By changing the frequency of the electric signal applied to the voicecoil 8, it is possible to drive either one or both of the diaphragm 18and the mechanical vibration system 6, such that the diaphragm 18produces a buzzer sound, melodies or communicant voice and themechanical vibration system 6 produces a vibration sensed by the body.That is, because it is possible to produce a vibration sensed by thebody, communicant voice, and a buzzer sound or melodies with a singleactuator 1, it is possible to reduce the number of mechanisms mounted inportable terminals.

However, when a portable terminal in which this electromagneticinduction actuator 1 is mounted is awaiting an incoming call, that is,when the electromagnetic induction actuator is not operating, a tap onthe outer case of the portable terminal will cause the mechanicalvibration system to oscillate and produce the sound of a snapped string(hereafter this sound is referred to as an extraneous tone). Thisextraneous tone may cause the user to sense a lack of rigidity in thecase of his portable terminal, or give the false impression of amalfunction or improper mounting of parts within the portable terminal.

For that reason, the present inventors have devised a portable terminalin which is mounted an extraneous tone reduction device to dampen thevibration of the mechanical vibration system. They have a further goalof providing an extraneous tone reduction device by an inexpensive andsimple means, and thereby prevent increases in the cost or size of theportable terminal.

DESCRIPTION OF INVENTION

This invention is a portable terminal in which is mounted anelectromagnetic induction actuator that has as its base a housing inwhich magnet with yoke and pole piece make up a magnetic circuit that issupported by leaf-spring to constitute mechanical vibration system,there being diaphragm fixed in open end of the housing, voice coilattached to the diaphragm, and terminal fittings that are placed onterminal seat projecting outward from side of the housing, the voicecoil being connected electrically to the terminal fittings, in which theelectromagnetic induction actuator have switching means that causescurrent to flow in the voice coil by short-circuiting the terminalfittings when the portable terminal is awaiting an incoming call.

This invention also provides a portable terminal in which is mounted anelectromagnetic induction actuator that has as its base a housing inwhich magnet with yoke and pole piece make up a magnetic circuit that issupported by leaf-spring to constitute mechanical vibration system,there being diaphragm fixed in open end of the housing, voice coilattached to the diaphragm, and terminal fittings that are placed onterminal seat projecting outward from side of the housing, the voicecoil being connected electrically to the terminal fittings, in whichamplifier that is electrically connected to the terminal fittings and isnormally set in operating state by application of a voltage, and whichadjusts the output signal by feedback of signal found on the terminalfittings when the portable terminal is awaiting an incoming call.

This invention also provides a portable terminal in which is mounted anelectromagnetic induction actuator as described in claim 2, in whichthere is signal generation source electrically connected to theamplifier, which outputs a constant-voltage signal and aconstant-frequency signal to the amplifier.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing the internal construction ofportable terminal of the first example of implementation of thisinvention.

FIG. 2 is a graph showing the oscillation characteristics of themechanical vibration system inside the electromagnetic inductionactuator as measured at the outer case of the terminal equipment.

FIG. 3 is an oblique sketch of the mechanical vibration system and voicecoil of the electromagnetic induction actuator when the mechanicalswitch is open.

FIG. 4 is an oblique sketch of the mechanical vibration system and voicecoil of the electromagnetic induction actuator when the mechanicalswitch is closed.

FIG. 5 is a circuit diagram showing the internal construction of aportable terminal in which is mounted an extraneous tone reductiondevice in which a transistor is used in the mechanical switch of FIG. 1.

FIG. 6 is a schematic circuit diagram showing the internal constructionof portable terminal of the second example of implementation of thisinvention.

FIG. 7 is a schematic circuit diagram showing the internal constructionof portable terminal of the third example of implementation of thisinvention.

FIG. 8 is a schematic oblique drawing showing the electromagneticinduction actuator.

OPTIMUM MODE TO IMPLEMENT INVENTION

First Example of Implementation: The first example of implementation ofthe portable terminal of this invention is explained in detail below,with reference to FIGS. 1 through 4. FIG. 1 is a schematic diagramshowing the internal construction of portable terminal of the firstexample of implementation of this invention, and FIG. 2 is a graphshowing the oscillation characteristics of the mechanical vibrationsystem inside the electromagnetic induction actuator as measured at theouter case of the terminal equipment. As shown in FIG. 1, anelectromagnetic induction actuator 1 and a mechanical switch 2 that isthe switching means that short circuits the terminal fittings 3, 3′ aremounted within the outer case 5, indicated by the broken line, of theportable terminal 4. The following explanation of this example ofimplementation is based on the assumption that the electromagneticinduction actuator 1 is not in the operating state; that is, theportable terminal 4 is in the state of awaiting an incoming call. Now,the internal structure, operation and functions of the electromagneticinduction actuator 1 are the same as shown in FIG. 8; duplicativeexplanation is omitted.

The principle behind production of an extraneous tone will be explainedfirst. In FIG. 1, the mechanical switch 2 is in the open state, which isequivalent to the internal structure of the conventional portableterminal. When the outer case 5 is tapped in this state, the vibrationof the case causes the mechanical vibration system within theelectromagnetic induction actuator 1 to vibrate. As described above, themechanical vibration system is flexibly supported by two leaf-springsuspensions, and so a graph of the oscillation characteristics of themechanical vibration system shows gradual convergence and attenuationover time. The broken line curve in FIG. 2 shows the oscillationcharacteristics measured through the outer case 5. Vibrating as shown bythe broken line curve, the mechanical vibration system causes the air toquiver, producing an extraneous tone similar to a snapped string.

Next, while explaining the principle of reduction of the extraneoustone, the structure and operation of a concrete device will beexplained. FIGS. 3 and 4 are oblique sketches that show the states ofthe mechanical vibration system and voice coil of the electromagneticinduction actuator. When the outer case is tapped as described above,the mechanical vibration system 6 vibrates up and down in the directionof arrow 7. With that, electromagnetic induction occurs between themagnetic circuit 9 of the mechanical vibration system 6 and the voicecoil 8 that is electrically connected to the terminal fittings, andinduced electromotive force is created in the voice coil 8. Because themechanical vibration system 6 vibrates up and down, the direction of theinduced electromotive force keeps changing back and forth with eachcycle.

When the mechanical switch 2 is open, as in FIG. 3, the terminalfittings (not illustrated) are opened and so the induced electromotiveforce generated in the voice coil 8 does not flow as an induced current.Consequently no magnetic field is produced by the induced current. Whenthe mechanical switch 2 is closed as in FIG. 4, however, there is aclosed circuit between the voice coil 8 and the mechanical switch 2, andso the induced current 10 flows through the voice coil 8 and generates amagnetic field 11. The direction of this magnetic field 11 counters thedirection of vibration of the magnetic circuit, and so the up and downoscillations of the mechanical vibration system are suppressed andconverge quickly. The curve of the oscillation characteristics, asmeasured through the outer case, is shown by the solid line in FIG. 2.As FIG. 2 indicates, the oscillation characteristics when the mechanicalswitch 2 is closed (the terminal fittings are short-circuited) convergeat zero more quickly than the oscillation characteristics when it isopen, and so the sense of reverberation in the audible period is greatlydiminished. In this way, the user's awareness is that the extraneoustone is reduced.

Now, the mechanical switch 2 can be made using a transistor as shown inFIG. 5, an FET or other semiconductor element with a switching action,or a relay or other excited contact device. It is also possible to forman analog switch of various semiconductor devices and use that as themechanical switch. It is also possible, needless to say, to obtain thesame effect using an IC that incorporates an analog switch.

Using this example of implementation, it is possible to reduce theextraneous tone when the portable terminal is awaiting an incoming call,and by limiting the additional parts required to realize the extraneoustone reduction device to the one mechanical switch, it is possible tominimize any increase to the size or cost of the portable terminal. Byusing a mechanical switch that is widely known and structure is simple,it is possible to provide a portable terminal in which is mounted anextraneous tone reduction device with a switching function that isinexpensive and highly reliable.

Second Example of Implementation: The second example of implementationof the portable terminal of this invention is explained in detail below,with reference to the circuit diagram of FIG. 6. Now, the internalstructure, operation and functions of the electromagnetic inductionactuator 1 are the same as shown in FIG. 8; duplicative explanation isomitted. The explanation of this example of implementation is based onthe assumption that the electromagnetic induction actuator 1 is not inthe operating state; that is, that the portable terminal 4 is in thestate of awaiting an incoming call. The extraneous tone reduction deviceof FIG. 6 comprises the electromagnetic induction actuator 1, and twoamplifiers 13, 13′ that are electrically connected to the terminalfitting 3 (and 3′) respectively.

Amplifiers have been mounted in conventional portable terminals as well,but when those terminals are in the state of awaiting an incoming call,the voltage to the amplifiers is turned down, and their function isessentially stopped. This example of implementation is set so thatvoltage is always applied to the amplifiers 13, 13′ and they are in anoperating state.

The operation of a portable terminal constituted in this way isexplained below. In a quiet state with no outside force applied to theouter case 5, there is no signal input to the amplifiers 13, 13′, and sothe voltage value of the output signals 15, 15′ is maintained at 0[V].The voltage value of the signal found at the terminal fitting 3 (and 3′)of the electromagnetic induction actuator 1 is also maintained at 0[V].When vibration is applied by a tap on the outer case 5, the vibration ispassed to the extraneous noise reduction device inside the outer case 5,and the mechanical vibration system (not illustrated) within theelectromagnetic induction actuator 1 vibrates.

Because of this vibration, there is electromagnetic induction betweenthe magnetic circuit of the mechanical vibration system and the voicecoil, and an induced electromagnetic force is generated in the voicecoil. When this induced electromagnetic force is found on the terminalfittings 3, 3′, the voltage value of one side or the other of signal 14,14′ changes from 0[V] to a value of V[V], for a voltage imbalancebetween the two input terminals. In this way the voltage value of thesignal 14 changes from 0[V] to V [V].

Then the signal 14 is input as feedback to the amplifier 13′; thevoltage value of the output signal 15′ changes to −V[V] and is input tothe terminal fitting 3′. In that way, a closed circuit is formed betweenthe voice coil (not illustrated) and the two amplifier circuits 13, 13′,the induction current flows in the voice coil and a magnetic field iscreated. After that, the direction of this magnetic field 11 suppressesthe oscillations of the mechanical vibration system and causeconvergence at zero, thus reducing the extraneous tone by the sameprinciple as in the first example of implementation.

In addition to that reduction of the extraneous tone, the operation ofthe amplifiers 13, 13′ in itself has the effect of reducing theextraneous tone. That operation is explained below. In FIG. 6 no signalis input to the amplifier 13 (that is, the input side of the amplifiercircuit 13 is normally 0[V]), and so the output signal 15 graduallychanges from V [V] to 0[V]. Because of this output signal 15 is appliedto the terminal fitting 15, signal 14 also changes to 0[V]. Then assignal 14 is fed back and input to the amplifier, the output. And signal14′ also changes to 0[V]. That is, the two amplifier circuits 13, 13′adjust their output signals 15, 15′ to 0[V], which restores the originalquiet state of the electromagnetic induction actuator, with the voltagevalues of the signals 14, 14′ returned to 0[V]. It can be seen from theabove that connecting amplifiers, which are normally set in theoperating state by application of a voltage, to the electromagneticinduction actuator is effective in reduction of the extraneous tone.

The oscillation characteristics of the mechanical vibration systemmeasured through the outer case 5 measure almost the same as the curveshown by the solid line in FIG. 2. Accordingly, the sense ofreverberation in the audible period is greatly diminished and in thisway, the user's awareness is that the extraneous tone is reduced.

Using this example of implementation, it is not necessary to add newequipment to the portable terminal, since amplifiers conventionallymounted in the portable terminal are used for reduction of theextraneous tone. There is, therefore, no need to increase the size orcost of the portable terminal. Because well known and structurallysimple amplifiers are used, it is possible to provide an extraneous tonereduction device of low cost and high operating reliability, and aportable terminal in which such a device is mounted.

Third Example of Implementation: The third example of implementation ofthe portable terminal of this invention is explained in detail next,with reference to the circuit diagram of FIG. 7. Now, parts andstructure that duplicate or overlap those of the second case ofimplementation above are omitted. In this example of implementation theextraneous tone reduction device has, in addition to the circuitconstitution shown in FIG. 6, a signal generator source 16 that iselectrically connected to one amplifier 13 to output a signal to it; thedevice is mounted inside the outer case 5 of the portable terminal 4. Inthis example of implementation too, the amplifiers 13, 13′ are alwaysset in an operating state with voltage applied, and the explanationassumes a state in which the electromagnetic induction actuator 1 is notoperating; that is, that the portable terminal 4 is in the state ofawaiting a call.

The following explanation concerns the overall operation of the portableterminal when the signal generation source 16 generates aconstant-voltage signal 17, and the portable terminal 4 in which thisdevice is mounted. The constant-voltage signal 17 is amplified by theamplifiers 13, 13′ and input to the terminal fittings 3, 3′ of theelectromagnetic induction actuator 1. The voltage value of the outputsignals 15, 15′ at that time is expressed as V[V] for convenience ofexplanation.

In a quiet state with no outside force applied to the outer case, thevoltage values of the signals 15, 15′ are maintained at V[V] and −V[V].Consequently, the voltage values of the signals 14, 14′ found on theterminal fittings 3, 3′ of the electromagnetic induction actuator 1 arealso maintained at V[V] and −V[V]. Tapping the outer case 5 in thisstate causes vibration that generates electromagnetic induction betweenthe magnetic circuit of the mechanical vibration system (notillustrated) and the voice coil (not illustrated), so that an inducedelectromotive force arises in the voice coil.

This electromotive force is found on the two terminal fittings 3, 3′that are electrically connected to the voice coil, and so the voltagevalue of one of the signals 14, 14′ found on the terminal fittings 3, 3′changes from V[V] to V′[V], and the voltage values of the signals 14,14′ are unbalanced between the two input terminals.

Then, as previously stated in the second example of implementation, aclosed circuit is formed between the voice coil (not illustrated) andthe two amplifiers 13, 13′, an induced current flows through the voicecoil, and a magnetic field is created, so that the vibration of themechanical vibration system is suppressed and converges on zero, and theextraneous tone is reduced.

Further, in addition to this extraneous tone reduction operation, thisexample of implementation makes it possible to achieve an extraneoustone reduction effect from the operation of the amplifiers 13, 13′. Thisoperation is explained below. According to FIG. 7, the input side ofamplifier 13 is always maintained at a fixed voltage value from theconstant-voltage signal 17, and so the output signal 15 graduallychanges from V′[V] to V[V]. Because of this output signal 15, the signal14 also changes to V[V]. Then, by inputting the signal 14 to theamplifier circuit 13′ as feedback, the output signal 15′ is changed to−V[V], and when the signal 15′ is applied, the signal 14′ also changesto −V[V]. In other words, the two amplifiers 13, 13′ adjust their outputsignals 15, 15′ to V[V] and −V[V], and by that means the electromagneticinduction actuator 1 is returned to its original quiet characteristics,with the signals 14, 14′ having voltage values of V[V] and −V[V]. It canbe seen from the above that connecting amplifiers, which are normallyset in the operating state by application of a voltage, to theelectromagnetic induction actuator and inputting a constant-voltagesignal to the amplifiers is effective in reduction of the extraneoustone.

The oscillation characteristics of the mechanical vibration systemmeasured through the outer case 5 measure almost the same as the curveshown by the solid line in FIG. 2. Accordingly, the sense ofreverberation in the audible period is greatly diminished and in thisway, the user's awareness is that the extraneous tone is reduced.

One standard for the voltage value of the constant-voltage signal 17 isto have a voltage value such that, when the signal 17 is amplified andinput to operate the electromagnetic induction actuator 1, it drives theelectromagnetic induction actuator 1 without the user of the portableterminal being aware of that operation. That is, the voltage valueshould be smaller than the voltage value that performs the incoming callnotification operation of the electromagnetic induction actuator 1(hereafter the operating voltage). However, the value of the operatingvoltage can vary, depending on the type, size, weight and model of theelectromagnetic induction actuator 1. Consequently, it is not possibleto make a blanket statement that the voltage value of theconstant-voltage signal should be less than any specific voltage. Asstated above, it is preferable to set that value with reference to theoperating voltage of the electromagnetic induction actuator 1.

Now, for the convenience of explanation, the third example ofimplementation has been explained only in the case of an inversionamplifier circuit using operational amplifiers. It is possible, however,to change the amplifier as long as it has the function of holding theoutput signal constant. The same effect can be had, needless to say, byreplacing the amplifiers with amplifiers created by connectingtransistors, FETs or other semiconductor elements.

In this example of implementation a constant-voltage signal is amplifiedand applied to the terminal fittings, but the same effect can be had byamplifying the voltage of a constant-frequency signal, which has a fixedfrequency, and applying that to the terminal fittings instead of aconstant-voltage signal. Now, the constant-frequency signal is producedby the signal generator 16.

One standard for the frequency range of the constant-frequency signal isto set the range that will allow operation at a level that will not benoticed by the user of the portable terminal 4 when the electromagneticinduction actuator 1 operates. The frequency should be set, therefore,outside the operating range of the electromagnetic induction actuator 1.However, that operating range will vary depending on the type, size,weight and model of the electromagnetic induction actuator 1; a blanketdecision is not possible, and no one specific frequency can be specifiedas the appropriate frequency rang for the constant-frequency signal. Asa guideline, it is preferable to set the range outside the 20[Hz] to20[kHz] range generally know as the frequency range audible to humans,but because the audible range varies from person to person, a blanketdecision is not possible. As stated above, it is preferable to decidethe range with reference to the operating range of the electromagneticinduction actuator 1; mounted in the portable terminal 4.

Using this example of implementation, amplifiers conventionally mountedin the portable terminal are used for reduction of the extraneous toneby means of constant operation. Adding no new parts to the portableterminal except a vibration generator, it is possible to reduce theextraneous tone while minimizing increases to the size or cost of theportable terminal.

POTENTIAL FOR INDUSTRIAL USE

Using this invention, it is possible to reduce the extraneous tone whena portable terminal is in the state of awaiting an incoming call, and itis also possible to realize an extraneous tone reduction device in whichonly one new part—a mechanical switch or a source of vibration—ismounted in the portable terminal, or to realize an extraneous tonereduction device that uses amplifiers already mounted in the portableterminal without mounting any new parts. It is possible, accordingly, tohold to a minimum any increase in the size or cost of the portableterminal, and to provide an inexpensive and highly reliable extraneoustone reduction device and a portable terminal in which such a device ismounted.

1. A portable communication terminal for receiving an incomingcommunication, the terminal having a compact electromagnetic inductionactuator for producing a vibration as well as an audible signal,comprising: a magnetic vibration system having a plate magnet, a yokeand a pole piece; a cylindrical housing enclosing an upper and a lowerleaf-spring suspension which sandwich vibration system; an audiblegenerator disposed on one end of the cylindrical housing, the audiblegenerator having a voice coil, a diaphragm attached to the voice coil; apair of input terminal disposed on the housing and connected to thevoice coil and the magnetic vibration system for conveying an electricalsignal having a frequency that produce a vibration in the magneticvibration system or the audible sound generator, depending on thefrequency of the electrical signal; and an individual amplifierconnected to the each input terminal and the amplifier is normally setin operating state by application of a voltage, and a signal from theinput terminal is fed to one of the amplifier for adjusting the outputsignal of the amplifier when the portable communication terminal isawaiting an incoming call.
 2. A portable communication terminal, asdescribed in claim 1, further comprising: a signal generation sourceelectrically connected to the amplifier for providing a constant-voltagesignal and a constant-frequency signal to the amplifier.
 3. A portablecommunication terminal for receiving an incoming communication, theterminal having an electromagnetic induction actuator for producing avibration as well as an audible signal, comprising: a magnetic vibrationsystem having a plate magnet, a yoke and a pole piece; a cylindricalhousing enclosing an upper and a lower leaf-spring suspension whichsandwich the magnetic vibration system; an audible sound generatordisposed on one end of the cylindrical housing, the sound generatorhaving a voice coil and a diaphragm attached to the voice coil; a pairof input terminal disposed on the housing and connected to the voicecoil and the magnetic vibration system for conveying an electricalsignal having a frequency that produces a vibration in the magneticvibration system or an audible sound in the round generator, dependingon the frequency of the electrical signal; and means forshort-circuiting the pair of input terminal so as to short circuit thevoice coil and to dampen the movement of the magnetic vibration system,when an incoming communication is not being received, so as to reduce aproduction of an extraneous tone in the voice coil.
 4. A portablecommunication terminal, as recited in claim 3, wherein the means forshort-circuiting is an electronic switch.
 5. A portable communicationterminal, as recited in claim 3, wherein the means for short-circuitingis an electro-mechanical switch.